/**
 * 求两个颜色之间的渐变值
 * @param {string} startColor 开始的颜色
 * @param {string} endColor 结束的颜色
 * @param {number} step 颜色等分的份额
 * */
export function colorGradient(
  startColor = "rgb(0, 0, 0)",
  endColor = "rgb(255, 255, 255)",
  step = 10
) {
  const startRGB = hexToRgb(startColor, false); // 转换为rgb数组模式
  const startR = startRGB[0];
  const startG = startRGB[1];
  const startB = startRGB[2];

  const endRGB = hexToRgb(endColor, false);
  const endR = endRGB[0];
  const endG = endRGB[1];
  const endB = endRGB[2];

  const sR = (endR - startR) / step; // 总差值
  const sG = (endG - startG) / step;
  const sB = (endB - startB) / step;
  const colorArr = [];
  for (let i = 0; i < step; i++) {
    // 计算每一步的hex值
    let hex = rgbToHex(
      `rgb(${Math.round(sR * i + startR)},${Math.round(
        sG * i + startG
      )},${Math.round(sB * i + startB)})`
    );
    // 确保第一个颜色值为startColor的值
    if (i === 0) hex = rgbToHex(startColor);
    // 确保最后一个颜色值为endColor的值
    if (i === step - 1) hex = rgbToHex(endColor);
    colorArr.push(hex);
  }
  return colorArr;
}

// 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
export function hexToRgb(sColor, str = true) {
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
  sColor = String(sColor).toLowerCase();
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = "#";
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));
      }
      sColor = sColorNew;
    }
    // 处理六位的颜色值
    const sColorChange = [];
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt(`0x${sColor.slice(i, i + 2)}`));
    }
    if (!str) {
      return sColorChange;
    }
    return `rgb(${sColorChange[0]},${sColorChange[1]},${sColorChange[2]})`;
  }
  if (/^(rgb|RGB)/.test(sColor)) {
    const arr = sColor.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",");
    return arr.map((val) => Number(val));
  }
  return sColor;
}

// 将rgb表示方式转换为hex表示方式
export function rgbToHex(rgb) {
  const _this = rgb;
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;

  if (/^(rgb|RGB)/.test(_this)) {
    const aColor = _this.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",");
    let strHex = "#";
    for (let i = 0; i < aColor.length; i++) {
      let hex = Number(aColor[i]).toString(16);
      hex = String(hex).length == 1 ? `${0}${hex}` : hex; // 保证每个rgb的值为2位
      if (hex === "0") {
        hex += hex;
      }
      strHex += hex;
    }
    if (strHex.length !== 7) {
      strHex = _this;
    }
    return strHex;
  }
  if (reg.test(_this)) {
    const aNum = _this.replace(/#/, "").split("");
    if (aNum.length === 6) {
      return _this;
    }
    if (aNum.length === 3) {
      let numHex = "#";
      for (let i = 0; i < aNum.length; i += 1) {
        numHex += aNum[i] + aNum[i];
      }
      return numHex;
    }
  } else {
    return _this;
  }
}

/**
 * JS颜色十六进制转换为rgb或rgba,返回的格式为 rgba（255，255，255，0.5）字符串
 * sHex为传入的十六进制的色值
 * alpha为rgba的透明度
 */
export function colorToRgba(color, alpha) {
  color = rgbToHex(color);
  // 十六进制颜色值的正则表达式
  const reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
  /* 16进制颜色转为RGB格式 */
  let sColor = String(color).toLowerCase();
  if (sColor && reg.test(sColor)) {
    if (sColor.length === 4) {
      let sColorNew = "#";
      for (let i = 1; i < 4; i += 1) {
        sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));
      }
      sColor = sColorNew;
    }
    // 处理六位的颜色值
    const sColorChange = [];
    for (let i = 1; i < 7; i += 2) {
      sColorChange.push(parseInt(`0x${sColor.slice(i, i + 2)}`));
    }
    // return sColorChange.join(',')
    return `rgba(${sColorChange.join(",")},${alpha})`;
  }

  return sColor;
}

export default {
  colorGradient,
  hexToRgb,
  rgbToHex,
  colorToRgba,
};
